hydrocarbonate – 1kg course (12-15 mm) is a pure natural product. It is used in Calciumreactors, and may be used in filters to increase the hardness of water, and as a substrate material in marine or Malawi/Tanganyika aquaria. A natural calcium-carbonic acid equilibrium is created in all aquariums with an alkaline pH value, and in a Calciumreactor supplied with CO2, the hydrocarbonate is completely dissolved to calcium bicarbonate, becoming available for assimilation by hard and many soft corals, sponges, echinoderms, etc. Hydrocarbonate is available in 2 grain sizes: medium (3-5mm) for Calciumreactors, and coarse (12-15mm) as filter material.